Hall effect converter construction



April 29, 1952 B. D. LEETE 2,594,939

HALL EFFECT CONVERTER CONSTRUCTION Filed June 6, 1950 Inventor": Bernard D. Lest-e,

Hi5 Attorney.

Patented Apr. 29, 1952 HALL EFFECT CONVERTER CONSTRUCTION Bernard D. Leete, Peabody, Mass., assignor to General Electric Company, a

New York My invention relates to Hall effect" converter construction and, more particularly, to a wiring arrangement for eliminating induced volta-es in the lead wires connected to a Hall effect plate employed in converters such as described in U. S. Patent 2,464,807 of Albert Hansen, Jr., assigned to the assignee of the present invention.

The aforementioned patent utilizes a phenomenon known as the Hall effect to generate an alternating voltage having an amplitude dependent upon a direct current. In employing this phenomenon, a thin semi-conductor plate su h, for example, as germanium, is disposed in an alternating magnetic field such that the field is perpendicular to the face of the plate. A direct currentis passed longitudinally through the plate perpendicular to the magnetic field and a voltage is developed between points in the plate which lie along a line mutually perpendicular to the path of the current and to the direction of the magnetic field. The intensity of the magnetic field is varied according to a sine wave with respect to time, and the amplitude of the sine wave of voltagedeveloped is related to the magnitude of the direct current. Consequently, a direct current may be converted to an alternating voltage having an amplitude dependent upon the magnitude of the direct current and having a frequency canal to the frequency of the changing magnetic field.

In a practical application of this converter, a diificulty is encountered in that voltages are induced in the lead wires connectin a direct current source to the plate, and also in the lead wires connecting the alternating voltage to a useful signal translating stage. These induced voltages having the frequency of the alternating magnetic field and, hence, having the same frequency as the generated alternating voltage cannot be filtered out in the signal translating stages. Consequently, these induced voltages should be minimized in the converter for m st applications. A pivoted conductor located in the air gap of the magnetic field producing means, such as described in the heretofore mentioned patent, provides means for compensating for these induced voltages, but has the disadvantage of necessitating a longer air ga and, hence, a

greater amount of power to produce the magnetic field.

It is, therefore, an object of my invention to provide an improved wiring arrangement for a Hall efiect converter in which these induced voltages are minimized.

In the attainment of the foregoin object, I

corporation of Application June 6, 1950;, Serial No. 166,515

1 Claim. (01. 321-45) 2 provide a wiring arrangement in which the lead wires to a Hall eifect plate are so arranged within the magnetic field that the voltage magnetically induced in one portion of the lead wire is small and is compensated. for by a voltage magnetically induced in another portion of the lead wire. Consequently, any voltage induced in these wires by the magnetic field is balanced out and, therefore, does not appear in the output voltage of the converter.

For additional objects and advantages, and for a better understanding of my invention, attention is now directed to the following description and accompanying drawing in which the features of my invention believed to be novel are particularly pointed out, in which Fig-1 is a preferred embodiment of my invention; and Fig. 2 is a echomatic electric diagram suitable to the arrangement of Fig. 1.

Referring to l, a thin Hall effect" disk 26 having a magnetic field passing perpendicularly to the face of the plate has mounted on opposite sides thereof terminals 27, 28, 29, and 3B. A dotted line 3| between terminals 21 and 29 represents the path of average current in plate 26 between terminals 21 and 29, and dotted line 32 represents the path of average current between terminals 25 and 39 through plate 26. A lead 33 and a lead 34 are connected between terminal 21 and the end terminals of a variable three-terminal resistor 35. Terminal 29 is connected by a lead 36 to an external circuit. A variable resistor Si is similarly connected to terminals 28 and 38. Considering terminals 21 and 28 and its associated potentiometer and lead wires, an alternating magnetic field induces a voltage in the loop composed of conductor 33 and current path SI, and another voltage is deveolped in the loop comprising conductor 34 and current path 3!. As shown in Fig. 2, the voltages in each loop, Va and Vb, establish opposite currents in conductor 36 which, by the proper adjustment of variable tap 38, may be balanced out.

This embodiment has the advantage that it may be used with laminated core electromagnets, and, because the lead wires do not extend over the face of the disk, the gap between the magnet poles may be made very small, thus reducing the power required to operate the magnet.

While this invention has been described by particular embodiments thereof, it will be understood that those skilled in the art may make many changes and modifications without departing from my invention. Therefore, by the appended claim, I intend to cover all such changes 3 and modifications which fall within the true spirit and scope of this invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

In combination, a magnetic field producing means comprising a core of magnetic material havin'gma. pair of poles separated, by an air gap and means for alternately magnetizing said core in opposite directions, a semi-conductor Hall plate having first and second mutually transverse.

axes and being disposed in said air gap such that the magnetic field locatedlbetweensaidflpolesis: in a direction perpendicularto each of said axes, a pair of conductors located on..-.0pp 0site'sides ofsaid plate and electrically connected to one extremity of said first transverse axis such that said conductors lie external togsaidc'plate and said poles on opposite sides of said plate, a pptenti:--

ometer being located on a line coinciding with said first axis, the position of said potentiometer being beyond the other extremity of said first axis, said conductors being connected to opposite ends of said potentiometer, and external circuit conductors connected to the other said extremity of said first axis and to an adjustable point on said, potentiometer.

BERNARD-D. LEETE.

10' REFERENCES CITED The following references are of record in the filer-of th is -patentr UNITED: STATES PATENTS 15 Number-- Name Date 1,892,826" B'ettison et a1. Jan. 3, 1933 $003,857 Flanders July 23, 1935 2,373,601 Robinson Apr. 10, 1945 23643807 Hansen Mar. 22, 1949 

